Air or water pumps generally installed on an aquarium are most likely using the city power as an energy source. If the city power fails for any reason, these pumps cease to work and thereby discontinue the supply of water or air to the aquarium. With such abrupt discontinuation of the supply of air or water, the aquatic animals may luckily enough may stay alive for 1 or 2 more hours if the city power was to resume supply at this time. But if the failure of power lasts longer than this the aquatic animals lives are threatened once the oxygen contained in the water is exhausted.
Bearing in mind the shortcoming specified above, the inventor has worked out, as a result of extensive research and experiment, an AC/DC automatic changeover and automatic charge device. This device is the parallel to the invention AC/DC Electro-Magnetic Device for Aeration Pump in Fish Globe or the like, of USA, Patent Right No. 4,636,695. The device of this invention is able to operate under the normal condition of an AC power supply, and in the meantime maintain automatic charge to a battery. If the AC power supply fails it automatically changes over to a DC power supply so as to maintain the function of the pumps without interruption.